Johnson & Starley Air Pressure Switch (Aps)

The air pressure switch Is a safety instrument which ensures the fan is in full working order. It ensures that, if the fan fails within the boiler, there would not be a build up of noxious gases with no means of venting them. The PCB closely monitors the air pressure switch to make sure it is fully functional before the unit is fired up, preventing the appliance from starting without one of its key safety devices.